Method for reporting channel state information having interference cancellation capability reflected therein, and apparatus therefor

ABSTRACT

A method for reporting channel state information (CSI) having interference cancellation capability reflected therein, and an apparatus therefor are disclosed. A method for reporting channel state information (CSI) to which interference cancellation capability is reflected in a wireless communication system is performed by a terminal and includes receiving one or more CSI process configurations including one or more CSI resource sets from a serving cell, wherein the CSI resource set is associated with a specific interference cell, detecting a dominant interference signal from a received signal and selecting a CSI resource set corresponding to the dominant interference signal, calculating CSI to which interference cancellation capability is reflected, using the selected CSI resource set or interference hypothesis (IH) information corresponding to the selected CSI resource set, and reporting the calculated CSI to the serving cell through a CSI process corresponding to the selected CSI resource set or the IH information.

This application claims the benefit of U.S. Provisional Application No. 61/975,007, filed on Apr. 4, 2014, which is hereby incorporated by reference as if fully set forth herein.

BACKGROUND OF THE INVENTION

Field of the Invention

The present invention relates to a wireless communication system and, more particularly, to a method for reporting channel state information (CSI) having interference cancellation capability reflected therein, and an apparatus therefor.

Discussion of the Related Art

Recently, various devices requiring machine-to-machine (M2M) communication and high data transfer rate, such as smartphones or tablet personal computers (PCs), have appeared and come into widespread use. This has rapidly increased the quantity of data which needs to be processed in a cellular network. In order to satisfy such rapidly increasing data throughput, recently, carrier aggregation (CA) technology which efficiently uses more frequency bands, cognitive ratio technology, multiple antenna (MIMO) technology for increasing data capacity in a restricted frequency, multiple-base-station cooperative technology, etc. have been highlighted. In addition, communication environments have evolved such that the density of accessible nodes is increased in the vicinity of a user equipment (UE). Here, the node includes one or more antennas and refers to a fixed point capable of transmitting/receiving radio frequency (RF) signals to/from the user equipment (UE). A communication system including high-density nodes may provide a communication service of higher performance to the UE by cooperation between nodes.

A multi-node coordinated communication scheme in which a plurality of nodes communicates with a user equipment (UE) using the same time-frequency resources has much higher data throughput than legacy communication scheme in which each node operates as an independent base station (BS) to communicate with the UE without cooperation.

A multi-node system performs coordinated communication using a plurality of nodes, each of which operates as a base station or an access point, an antenna, an antenna group, a remote radio head (RRH), and a remote radio unit (RRU). Unlike the conventional centralized antenna system in which antennas are concentrated at a base station (BS), nodes are spaced apart from each other by a predetermined distance or more in the multi-node system. The nodes can be managed by one or more base stations or base station controllers which control operations of the nodes or schedule data transmitted/received through the nodes. Each node is connected to a base station or a base station controller which manages the node through a cable or a dedicated line.

The multi-node system can be considered as a kind of Multiple Input Multiple Output (MIMO) system since dispersed nodes can communicate with a single UE or multiple UEs by simultaneously transmitting/receiving different data streams. However, since the multi-node system transmits signals using the dispersed nodes, a transmission area covered by each antenna is reduced compared to antennas included in the conventional centralized antenna system. Accordingly, transmit power required for each antenna to transmit a signal in the multi-node system can be reduced compared to the conventional centralized antenna system using MIMO. In addition, a transmission distance between an antenna and a UE is reduced to decrease in pathloss and enable rapid data transmission in the multi-node system. This can improve transmission capacity and power efficiency of a cellular system and meet communication performance having relatively uniform quality regardless of UE locations in a cell. Further, the multi-node system reduces signal loss generated during transmission since base station(s) or base station controller(s) connected to a plurality of nodes transmit/receive data in cooperation with each other. When nodes spaced apart by over a predetermined distance perform coordinated communication with a UE, correlation and interference between antennas are reduced. Therefore, a high signal to interference-plus-noise ratio (SINR) can be obtained according to the multi-node coordinated communication scheme.

Owing to the above-mentioned advantages of the multi-node system, the multi-node system is used with or replaces the conventional centralized antenna system to become a new foundation of cellular communication in order to reduce base station cost and backhaul network maintenance cost while extending service coverage and improving channel capacity and SINR in next-generation mobile communication systems.

SUMMARY OF THE INVENTION

Accordingly, the present invention is directed to a method for reporting channel state information (CSI) having interference cancellation capability reflected therein, and an apparatus therefor which substantially obviate one or more problems due to limitations and disadvantages of the related art.

An object of the present invention is to provide a method for reporting channel state information (CSI) having interference cancellation capability reflected therein.

Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, a method for reporting channel state information (CSI) to which interference cancellation capability is reflected in a wireless communication system is performed by a terminal and includes receiving one or more CSI process configurations including one or more CSI resource sets from a serving cell, wherein the CSI resource set is associated with a specific interference cell, detecting a dominant interference signal from a received signal and selecting a CSI resource set corresponding to the dominant interference signal, calculating CSI to which interference cancellation capability is reflected, using the selected CSI resource set or interference hypothesis (IH) information corresponding to the selected CSI resource set, and reporting the calculated CSI to the serving cell through a CSI process corresponding to the selected CSI resource set or the IH information, wherein the CSI resource set includes CSI-reference signal (RS) configuration information of the serving cell, cell-specific RS (CRS) or CSI-RS configuration information of the specific interference cell, and CSI-interference measurement (IM) resource information, and wherein the IH information includes information about transmission scheme of interference signal.

Additionally or alternatively, the IH information may be provided as a map consisting of N or fewer IH elements for L timings.

Additionally or alternatively, the method may further include transmitting an index of the selected CSI resource set to the serving cell.

Additionally or alternatively, the method may further include receiving an indicator indicating whether the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.

Additionally or alternatively, the method may further include receiving information about an individual element of the CSI to which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.

Additionally or alternatively, the method may further include receiving information about a combination of individual elements of the CSI to which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.

Additionally or alternatively, the method may further include receiving information about a time or frequency resource in which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell, and the information about the time or frequency resource may be provided per CSI resource set.

Additionally or alternatively, the method may further include receiving IH information corresponding to each of the CSI resource sets.

Additionally or alternatively, the method may further include receiving relationship information between the IH information and the CSI process configurations.

In another aspect of the present invention, a terminal configured to report channel state information (CSI) in a wireless communication system includes a radio frequency (RF) unit, and a processor configured to control the RF unit, wherein the processor is further configured to receive one or more CSI process configurations including one or more CSI resource sets from a serving cell, wherein the CSI resource set is associated with a specific interference cell, to detect a dominant interference signal from a received signal and select a CSI resource set corresponding to the dominant interference signal, to calculate CSI to which interference cancellation capability is reflected, using the selected CSI resource set or interference hypothesis (IH) information corresponding to the selected CSI resource set, and to report the calculated CSI to the serving cell through a CSI process corresponding to the selected CSI resource set or the IH information, wherein the CSI resource set includes CSI-reference signal (RS) configuration information of the serving cell, cell-specific RS (CRS) or CSI-RS configuration information of the specific interference cell, and CSI-interference measurement (IM) resource information, and wherein the IH information includes information about transmission scheme of interference signal.

Additionally or alternatively, the IH information may be provided as a map consisting of N or fewer IH elements for L timings.

Additionally or alternatively, the processor may be further configured to transmit an index of the selected CSI resource set to the serving cell.

Additionally or alternatively, the processor may be further configured to receive an indicator indicating whether the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.

Additionally or alternatively, the processor may be further configured to receive information about an individual element of the CSI to which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.

Additionally or alternatively, the processor may be further configured to receive information about a combination of individual elements of the CSI to which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.

Additionally or alternatively, the processor may be further configured to receive information about a time or frequency resource in which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell, and the information about the time or frequency resource may be provided per CSI resource set.

Additionally or alternatively, the processor may be further configured to receive IH information corresponding to each of the CSI resource sets.

Additionally or alternatively, the processor may be further configured to receive relationship information between the IH information and the CSI process configurations.

It is to be understood that both the foregoing general description and the following detailed description of the present invention are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are included to provide a further understanding of the invention and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the invention and together with the description serve to explain the principle of the invention. In the drawings:

FIG. 1 illustrates an exemplary radio frame structure in a wireless communication system;

FIG. 2 illustrates an exemplary structure of a downlink/uplink (DL/UL) slot in a wireless communication system;

FIG. 3 illustrates an exemplary structure of a DL subframe in a 3^(rd) Generation Partnership project (3GPP) Long Term Evolution (LTE)/LTE-Advanced (LTE-A) system;

FIG. 4 illustrates an exemplary structure of a UL subframe in the 3GPP LTE/LTE-A system;

FIG. 5 illustrates an interference environment in a multi-cell environment;

FIG. 6 illustrates a CSI process including one or more CSI resource sets according to an embodiment of the present invention;

FIG. 7 illustrates a CSI feedback scheme according to an embodiment of the present invention;

FIG. 8 illustrates a CSI feedback scheme according to an embodiment of the present invention;

FIG. 9 illustrates operation according to an embodiment of the present invention; and

FIG. 10 is a block diagram of devices according to embodiment(s) of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings. The accompanying drawings illustrate exemplary embodiments of the present invention and provide a more detailed description of the present invention. However, the scope of the present invention should not be limited thereto.

In some cases, to prevent the concept of the present invention from being ambiguous, structures and apparatuses of the known art will be omitted, or will be shown in the form of a block diagram based on main functions of each structure and apparatus. Also, wherever possible, the same reference numbers will be used throughout the drawings and the specification to refer to the same or like parts.

In the present invention, a user equipment (UE) is fixed or mobile. The UE is a device that transmits and receives user data and/or control information by communicating with a base station (BS). The term ‘UE’ may be replaced with ‘terminal equipment’, ‘Mobile Station (MS)’, ‘Mobile Terminal (MT)’, ‘User Terminal (UT)’, ‘Subscriber Station (SS)’, ‘wireless device’, ‘Personal Digital Assistant (PDA)’, ‘wireless modem’, ‘handheld device’, etc. A BS is typically a fixed station that communicates with a UE and/or another BS. The BS exchanges data and control information with a UE and another BS. The term ‘BS’ may be replaced with ‘Advanced Base Station (ABS)’, ‘Node B’, ‘evolved-Node B (eNB)’, ‘Base Transceiver System (BTS)’, ‘Access Point (AP)’, ‘Processing Server (PS)’, etc. In the following description, BS is commonly called eNB.

In the present invention, a node refers to a fixed point capable of transmitting/receiving a radio signal to/from a UE by communication with the UE. Various eNBs can be used as nodes. For example, a node can be a BS, NB, eNB, pico-cell eNB (PeNB), home eNB (HeNB), relay, repeater, etc. Furthermore, a node may not be an eNB. For example, a node can be a radio remote head (RRH) or a radio remote unit (RRU). The RRH and RRU have power levels lower than that of the eNB. Since the RRH or RRU (referred to as RRH/RRU hereinafter) is connected to an eNB through a dedicated line such as an optical cable in general, cooperative communication according to RRH/RRU and eNB can be smoothly performed compared to cooperative communication according to eNBs connected through a wireless link. At least one antenna is installed per node. An antenna may refer to an antenna port, a virtual antenna or an antenna group. A node may also be called a point. Unlink a conventional centralized antenna system (CAS) (i.e. single node system) in which antennas are concentrated in an eNB and controlled an eNB controller, plural nodes are spaced apart at a predetermined distance or longer in a multi-node system. The plural nodes can be managed by one or more eNBs or eNB controllers that control operations of the nodes or schedule data to be transmitted/received through the nodes. Each node may be connected to an eNB or eNB controller managing the corresponding node via a cable or a dedicated line. In the multi-node system, the same cell identity (ID) or different cell IDs may be used for signal transmission/reception through plural nodes. When plural nodes have the same cell ID, each of the plural nodes operates as an antenna group of a cell. If nodes have different cell IDs in the multi-node system, the multi-node system can be regarded as a multi-cell (e.g., macro-cell/femto-cell/pico-cell) system. When multiple cells respectively configured by plural nodes are overlaid according to coverage, a network configured by multiple cells is called a multi-tier network. The cell ID of the RRH/RRU may be identical to or different from the cell ID of an eNB. When the RRH/RRU and eNB use different cell IDs, both the RRH/RRU and eNB operate as independent eNBs.

A communication scheme through which signals are transmitted/received via plural transmit (Tx)/receive (Rx) nodes, signals are transmitted/received via at least one node selected from plural Tx/Rx nodes, or a node transmitting a downlink signal is discriminated from a node transmitting an uplink signal is called multi-eNB MIMO or CoMP (Coordinated Multi-Point Tx/Rx). Coordinated transmission schemes from among CoMP communication schemes can be categorized into JP (Joint Processing) and scheduling coordination. The former may be divided into JT (Joint Transmission)/JR (Joint Reception) and DPS (Dynamic Point Selection) and the latter may be divided into CS (Coordinated Scheduling) and CB (Coordinated Beamforming) DPS may be called DCS (Dynamic Cell Selection). When JP is performed, more various communication environments can be generated, compared to other CoMP schemes. JT refers to a communication scheme by which plural nodes transmit the same stream to a UE and JR refers to a communication scheme by which plural nodes receive the same stream from the UE. The UE/eNB combine signals received from the plural nodes to restore the stream. In the case of JT/JR, signal transmission reliability can be improved according to transmit diversity since the same stream is transmitted from/to plural nodes. DPS refers to a communication scheme by which a signal is transmitted/received through a node selected from plural nodes according to a specific rule. In the case of DPS, signal transmission reliability can be improved because a node having a good channel state between the node and a UE is selected as a communication node.

In the present invention, a cell refers to a specific geographical area in which one or more nodes provide communication services. Accordingly, communication with a specific cell may mean communication with an eNB or a node providing communication services to the specific cell. A downlink/uplink signal of a specific cell refers to a downlink/uplink signal from/to an eNB or a node providing communication services to the specific cell. A cell providing uplink/downlink communication services to a UE is called a serving cell. Furthermore, channel status/quality of a specific cell refers to channel status/quality of a channel or a communication link generated between an eNB or a node providing communication services to the specific cell and a UE. In 3GPP LTE-A systems, a UE can measure downlink channel state from a specific node using one or more CSI-RSs (Channel State Information Reference Signals) transmitted through antenna port(s) of the specific node on a CSI-RS resource allocated to the specific node. In general, neighboring nodes transmit CSI-RS resources on orthogonal CSI-RS resources. When CSI-RS resources are orthogonal, this means that the CSI-RS resources have different subframe configurations and/or CSI-RS sequences which specify subframes to which CSI-RSs are allocated according to CSI-RS resource configurations, subframe offsets and transmission periods, etc. which specify symbols and subcarriers carrying the CSI RSs.

In the present invention, PDCCH (Physical Downlink Control Channel)/PCFICH (Physical Control Format Indicator Channel)/PHICH (Physical Hybrid automatic repeat request Indicator Channel)/PDSCH (Physical Downlink Shared Channel) refer to a set of time-frequency resources or resource elements respectively carrying DCI (Downlink Control Information)/CFI (Control Format Indicator)/downlink ACK/NACK (Acknowledgement/Negative ACK)/downlink data. In addition, PUCCH (Physical Uplink Control Channel)/PUSCH (Physical Uplink Shared Channel)/PRACH (Physical Random Access Channel) refer to sets of time-frequency resources or resource elements respectively carrying UCI (Uplink Control Information)/uplink data/random access signals. In the present invention, a time-frequency resource or a resource element (RE), which is allocated to or belongs to PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH, is referred to as a PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH RE or PDCCH/PCFICH/PHICH/PDSCH/PUCCH/PUSCH/PRACH resource. In the following description, transmission of PUCCH/PUSCH/PRACH by a UE is equivalent to transmission of uplink control information/uplink data/random access signal through or on PUCCH/PUSCH/PRACH. Furthermore, transmission of PDCCH/PCFICH/PHICH/PDSCH by an eNB is equivalent to transmission of downlink data/control information through or on PDCCH/PCFICH/PHICH/PDSCH.

FIG. 1 illustrates an exemplary radio frame structure used in a wireless communication system. FIG. 1(a) illustrates a frame structure for frequency division duplex (FDD) used in 3GPP LTE/LTE-A and FIG. 1(b) illustrates a frame structure for time division duplex (TDD) used in 3GPP LTE/LTE-A.

Referring to FIG. 1, a radio frame used in 3GPP LTE/LTE-A has a length of 10 ms (307200Ts) and includes 10 subframes in equal size. The 10 subframes in the radio frame may be numbered. Here, Ts denotes sampling time and is represented as Ts=1/(2048*15 kHz). Each subframe has a length of 1 ms and includes two slots. 20 slots in the radio frame can be sequentially numbered from 0 to 19. Each slot has a length of 0.5 ms. A time for transmitting a subframe is defined as a transmission time interval (TTI). Time resources can be discriminated by a radio frame number (or radio frame index), subframe number (or subframe index) and a slot number (or slot index).

The radio frame can be configured differently according to duplex mode. Downlink transmission is discriminated from uplink transmission by frequency in FDD mode, and thus the radio frame includes only one of a downlink subframe and an uplink subframe in a specific frequency band. In TDD mode, downlink transmission is discriminated from uplink transmission by time, and thus the radio frame includes both a downlink subframe and an uplink subframe in a specific frequency band.

Table 1 shows DL-UL configurations of subframes in a radio frame in the TDD mode.

TABLE 1 Downlink- DL-UL to-Uplink configu- Switch-point Subframe number ration periodicity 0 1 2 3 4 5 6 7 8 9 0 5 ms D S U U U D S U U U 1 5 ms D S U U D D S U U D 2 5 ms D S U D D D S U D D 3 10 ms D S U U U D D D D D 4 10 ms D S U U D D D D D D 5 10 ms D S U D D D D D D D 6 5 ms D S U U U D S U U D

In Table 1, D denotes a downlink subframe, U denotes an uplink subframe and S denotes a special subframe. The special subframe includes three fields of DwPTS (Downlink Pilot TimeSlot), GP (Guard Period), and UpPTS (Uplink Pilot TimeSlot). DwPTS is a period reserved for downlink transmission and UpPTS is a period reserved for uplink transmission. Table 2 shows special subframe configuration.

TABLE 2 Normal cyclic prefix in downlink Extended cyclic prefix in downlink Special UpPTS UpPTS subframe Normal Extended Normal Extended configu- cyclic prefix cyclic prefix cyclic prefix cyclic prefix ration DwPTS in uplink in uplink DwPTS in uplink in uplink 0  6592 · T_(s) 2192 · T_(s) 2560 · T_(s)  7680 · T_(s) 2192 · T_(s) 2560 · T_(s) 1 19760 · T_(s) 20480 · T_(s) 2 21952 · T_(s) 23040 · T_(s) 3 24144 · T_(s) 25600 · T_(s) 4 26336 · T_(s)  7680 · T_(s) 4384 · T_(s) 5120 · T_(s) 5  6592 · T_(s) 4384 · T_(s) 5120 · T_(s) 20480 · T_(s) 6 19760 · T_(s) 23040 · T_(s) 7 21952 · T_(s) 12800 · T_(s) 8 24144 · T_(s) — — — 9 13168 · T_(s) — — —

FIG. 2 illustrates an exemplary downlink/uplink slot structure in a wireless communication system. Particularly, FIG. 2 illustrates a resource grid structure in 3GPP LTE/LTE-A. A resource grid is present per antenna port.

Referring to FIG. 2, a slot includes a plurality of OFDM (Orthogonal Frequency Division Multiplexing) symbols in the time domain and a plurality of resource blocks (RBs) in the frequency domain. An OFDM symbol may refer to a symbol period. A signal transmitted in each slot may be represented by a resource grid composed of N_(RB) ^(DL/UL)*N_(sc) ^(RB) subcarriers and N_(symb) ^(DL/UL) OFDM symbols. Here, N_(RB) ^(DL) denotes the number of RBS in a downlink slot and N_(RB) ^(UL) denotes the number of RBs in an uplink slot. N_(RB) ^(DL) and N_(RB) ^(UL) respectively depend on a DL transmission bandwidth and a UL transmission bandwidth. N_(symb) ^(DL) denotes the number of OFDM symbols in the downlink slot and N_(symb) ^(UL) denotes the number of OFDM symbols in the uplink slot. In addition, N_(sc) ^(RB) denotes the number of subcarriers constructing one RB.

An OFDM symbol may be called an SC-FDM (Single Carrier Frequency Division Multiplexing) symbol according to multiple access scheme. The number of OFDM symbols included in a slot may depend on a channel bandwidth and the length of a cyclic prefix (CP). For example, a slot includes 7 OFDM symbols in the case of normal CP and 6 OFDM symbols in the case of extended CP. While FIG. 2 illustrates a subframe in which a slot includes 7 OFDM symbols for convenience, embodiments of the present invention can be equally applied to subframes having different numbers of OFDM symbols.

Referring to FIG. 2, each OFDM symbol includes N_(RB) ^(DL/UL)*N_(sc) ^(RB) subcarriers in the frequency domain. Subcarrier types can be classified into a data subcarrier for data transmission, a reference signal subcarrier for reference signal transmission, and null subcarriers for a guard band and a direct current (DC) component. The null subcarrier for a DC component is a subcarrier remaining unused and is mapped to a carrier frequency (f0) during OFDM signal generation or frequency up-conversion. The carrier frequency is also called a center frequency.

An RB is defined by N_(symb) ^(DL/UL) (e.g., 7) consecutive OFDM symbols in the time domain and N_(sc) ^(RB) (e.g., 12) consecutive subcarriers in the frequency domain. For reference, a resource composed by an OFDM symbol and a subcarrier is called a resource element (RE) or a tone. Accordingly, an RB is composed of N_(symb) ^(DL/UL)*N_(sc) ^(RB) REs. Each RE in a resource grid can be uniquely defined by an index pair (k, l) in a slot. Here, k is an index in the range of 0 to N_(symb) ^(DL/UL)*N_(sc) ^(RB)−1 in the frequency domain and 1 is an index in the range of 0 to N_(symb) ^(DL/UL)−1.

Two RBs that occupy N_(sc) ^(RB) consecutive subcarriers in a subframe and respectively disposed in two slots of the subframe are called a physical resource block (PRB) pair. Two RBs constituting a PRB pair have the same PRB number (or PRB index). A virtual resource block (VRB) is a logical resource allocation unit for resource allocation. The VRB has the same size as that of the PRB. The VRB may be divided into a localized VRB and a distributed VRB depending on a mapping scheme of VRB into PRB. The localized VRBs are mapped into the PRBs, whereby VRB number (VRB index) corresponds to PRB number. That is, nPRB=nVRB is obtained. Numbers are given to the localized VRBs from 0 to N_(VRB) ^(DL)−1 and N_(VRB) ^(DL)=N_(RB) ^(DL) is obtained. Accordingly, according to the localized mapping scheme, the VRBs having the same VRB number are mapped into the PRBs having the same PRB number at the first slot and the second slot. On the other hand, the distributed VRBs are mapped into the PRBs through interleaving. Accordingly, the VRBs having the same VRB number may be mapped into the PRBs having different PRB numbers at the first slot and the second slot. Two PRBs, which are respectively located at two slots of the subframe and have the same VRB number, will be referred to as a pair of VRBs.

FIG. 3 illustrates a downlink (DL) subframe structure used in 3GPP LTE/LTE-A.

Referring to FIG. 3, a DL subframe is divided into a control region and a data region. A maximum of three (four) OFDM symbols located in a front portion of a first slot within a subframe correspond to the control region to which a control channel is allocated. A resource region available for PDCCH transmission in the DL subframe is referred to as a PDCCH region hereinafter. The remaining OFDM symbols correspond to the data region to which a physical downlink shared chancel (PDSCH) is allocated. A resource region available for PDSCH transmission in the DL subframe is referred to as a PDSCH region hereinafter. Examples of downlink control channels used in 3GPP LTE include a physical control format indicator channel (PCFICH), a physical downlink control channel (PDCCH), a physical hybrid ARQ indicator channel (PHICH), etc. The PCFICH is transmitted at a first OFDM symbol of a subframe and carries information regarding the number of OFDM symbols used for transmission of control channels within the subframe. The PHICH is a response of uplink transmission and carries an HARQ acknowledgment (ACK)/negative acknowledgment (NACK) signal.

Control information carried on the PDCCH is called downlink control information (DCI). The DCI contains resource allocation information and control information for a UE or a UE group. For example, the DCI includes a transport format and resource allocation information of a downlink shared channel (DL-SCH), a transport format and resource allocation information of an uplink shared channel (UL-SCH), paging information of a paging channel (PCH), system information on the DL-SCH, information about resource allocation of an upper layer control message such as a random access response transmitted on the PDSCH, a transmit control command set with respect to individual UEs in a UE group, a transmit power control command, information on activation of a voice over IP (VoIP), downlink assignment index (DAI), etc. The transport format and resource allocation information of the DL-SCH are also called DL scheduling information or a DL grant and the transport format and resource allocation information of the UL-SCH are also called UL scheduling information or a UL grant. The size and purpose of DCI carried on a PDCCH depend on DCI format and the size thereof may be varied according to coding rate. Various formats, for example, formats 0 and 4 for uplink and formats 1, 1A, 1B, 1C, 1D, 2, 2A, 2B, 2C, 3 and 3A for downlink, have been defined in 3GPP LTE. Control information such as a hopping flag, information on RB allocation, modulation coding scheme (MCS), redundancy version (RV), new data indicator (NDI), information on transmit power control (TPC), cyclic shift demodulation reference signal (DMRS), UL index, channel quality information (CQI) request, DL assignment index, HARQ process number, transmitted precoding matrix indicator (TPMI), precoding matrix indicator (PMI), etc. is selected and combined based on DCI format and transmitted to a UE as DCI.

In general, a DCI format for a UE depends on transmission mode (TM) set for the UE. In other words, only a DCI format corresponding to a specific TM can be used for a UE configured in the specific TM.

A PDCCH is transmitted on an aggregation of one or several consecutive control channel elements (CCEs). The CCE is a logical allocation unit used to provide the PDCCH with a coding rate based on a state of a radio channel. The CCE corresponds to a plurality of resource element groups (REGs). For example, a CCE corresponds to 9 REGs and an REG corresponds to 4 REs. 3GPP LTE defines a CCE set in which a PDCCH can be located for each UE. A CCE set from which a UE can detect a PDCCH thereof is called a PDCCH search space, simply, search space. An individual resource through which the PDCCH can be transmitted within the search space is called a PDCCH candidate. A set of PDCCH candidates to be monitored by the UE is defined as the search space. In 3GPP LTE/LTE-A, search spaces for DCI formats may have different sizes and include a dedicated search space and a common search space. The dedicated search space is a UE-specific search space and is configured for each UE. The common search space is configured for a plurality of UEs. Aggregation levels defining the search space is as follows.

TABLE 3 Search Space Aggregation Size Number of PDCCH Type Level L [in CCEs] candidates M^((L)) UE-specific 1 6 6 2 12 6 4 8 2 8 16 2 Common 4 16 4 8 16 2

A PDCCH candidate corresponds to 1, 2, 4 or 8 CCEs according to CCE aggregation level. An eNB transmits a PDCCH (DCI) on an arbitrary PDCCH candidate with in a search space and a UE monitors the search space to detect the PDCCH (DCI). Here, monitoring refers to attempting to decode each PDCCH in the corresponding search space according to all monitored DCI formats. The UE can detect the PDCCH thereof by monitoring plural PDCCHs. Since the UE does not know the position in which the PDCCH thereof is transmitted, the UE attempts to decode all PDCCHs of the corresponding DCI format for each subframe until a PDCCH having the ID thereof is detected. This process is called blind detection (or blind decoding (BD)).

The eNB can transmit data for a UE or a UE group through the data region. Data transmitted through the data region may be called user data. For transmission of the user data, a physical downlink shared channel (PDSCH) may be allocated to the data region. A paging channel (PCH) and downlink-shared channel (DL-SCH) are transmitted through the PDSCH. The UE can read data transmitted through the PDSCH by decoding control information transmitted through a PDCCH. Information representing a UE or a UE group to which data on the PDSCH is transmitted, how the UE or UE group receives and decodes the PDSCH data, etc. is included in the PDCCH and transmitted. For example, if a specific PDCCH is CRC (cyclic redundancy check)-masked having radio network temporary identify (RNTI) of “A” and information about data transmitted using a radio resource (e.g., frequency position) of “B” and transmission format information (e.g., transport block size, modulation scheme, coding information, etc.) of “C” is transmitted through a specific DL subframe, the UE monitors PDCCHs using RNTI information and a UE having the RNTI of “A” detects a PDCCH and receives a PDSCH indicated by “B” and “C” using information about the PDCCH.

A reference signal (RS) to be compared with a data signal is necessary for the UE to demodulate a signal received from the eNB. A reference signal refers to a predetermined signal having a specific waveform, which is transmitted from the eNB to the UE or from the UE to the eNB and known to both the eNB and UE. The reference signal is also called a pilot. Reference signals are categorized into a cell-specific RS shared by all UEs in a cell and a modulation RS (DM RS) dedicated for a specific UE. A DM RS transmitted by the eNB for demodulation of downlink data for a specific UE is called a UE-specific RS. Both or one of DM RS and CRS may be transmitted on downlink. When only the DM RS is transmitted without CRS, an RS for channel measurement needs to be additionally provided because the DM RS transmitted using the same precoder as used for data can be used for demodulation only. For example, in 3GPP LTE(-A), CSI-RS corresponding to an additional RS for measurement is transmitted to the UE such that the UE can measure channel state information. CSI-RS is transmitted in each transmission period corresponding to a plurality of subframes based on the fact that channel state variation with time is not large, unlike CRS transmitted per subframe.

FIG. 4 illustrates an exemplary uplink subframe structure used in 3GPP LTE/LTE-A.

Referring to FIG. 4, a UL subframe can be divided into a control region and a data region in the frequency domain. One or more PUCCHs (physical uplink control channels) can be allocated to the control region to carry uplink control information (UCI). One or more PUSCHs (Physical uplink shared channels) may be allocated to the data region of the UL subframe to carry user data.

In the UL subframe, subcarriers spaced apart from a DC subcarrier are used as the control region. In other words, subcarriers corresponding to both ends of a UL transmission bandwidth are assigned to UCI transmission. The DC subcarrier is a component remaining unused for signal transmission and is mapped to the carrier frequency f0 during frequency up-conversion. A PUCCH for a UE is allocated to an RB pair belonging to resources operating at a carrier frequency and RBs belonging to the RB pair occupy different subcarriers in two slots. Assignment of the PUCCH in this manner is represented as frequency hopping of an RB pair allocated to the PUCCH at a slot boundary. When frequency hopping is not applied, the RB pair occupies the same subcarrier.

The PUCCH can be used to transmit the following control information.

-   -   Scheduling Request (SR): This is information used to request a         UL-SCH resource and is transmitted using On-Off Keying (OOK)         scheme.     -   HARQ ACK/NACK: This is a response signal to a downlink data         packet on a PDSCH and indicates whether the downlink data packet         has been successfully received. A 1-bit ACK/NACK signal is         transmitted as a response to a single downlink codeword and a         2-bit ACK/NACK signal is transmitted as a response to two         downlink codewords. HARQ-ACK responses include positive ACK         (ACK), negative ACK (NACK), discontinuous transmission (DTX) and         NACK/DTX. Here, the term HARQ-ACK is used interchangeably with         the term HARQ ACK/NACK and ACK/NACK.     -   Channel State Indicator (CSI): This is feedback information         about a downlink channel. Feedback information regarding MIMO         includes a rank indicator (RI) and a precoding matrix indicator         (PMI).

The quantity of control information (UCI) that a UE can transmit through a subframe depends on the number of SC-FDMA symbols available for control information transmission. The SC-FDMA symbols available for control information transmission correspond to SC-FDMA symbols other than SC-FDMA symbols of the subframe, which are used for reference signal transmission. In the case of a subframe in which a sounding reference signal (SRS) is configured, the last SC-FDMA symbol of the subframe is excluded from the SC-FDMA symbols available for control information transmission. A reference signal is used to detect coherence of the PUCCH. The PUCCH supports various formats according to information transmitted thereon. Table 4 shows the mapping relationship between PUCCH formats and UCI in LTE/LTE-A.

TABLE 4 Number of bits per PUCCH Modulation subframe, format scheme M_(bit) Usage Etc. 1 N/A N/A SR (Scheduling Request) 1a BPSK 1 ACK/NACK or One codeword SR + ACK/NACK 1b QPSK 2 ACK/NACK or Two codeword SR + ACK/NACK 2 QPSK 20 CQI/PMI/RI Joint coding ACK/NACK (extended CP) 2a QPSK + 21 CQI/PMI/RI + Normal CP BPSK ACK/NACK only 2b QPSK + 22 CQI/PMI/RI + Normal CP QPSK ACK/NACK only 3 QPSK 48 ACK/NACK or SR + ACK/NACK or CQI/PMI/RI + ACK/NACK

Referring to Table 4, PUCCH formats 1/1a/1b are used to transmit ACK/NACK information, PUCCH format 2/2a/2b are used to carry CSI such as CQI/PMI/RI and PUCCH format 3 is used to transmit ACK/NACK information.

Reference Signal (RS)

When a packet is transmitted in a wireless communication system, signal distortion may occur during transmission since the packet is transmitted through a radio channel. To correctly receive a distorted signal at a receiver, the distorted signal needs to be corrected using channel information. To detect channel information, a signal known to both a transmitter and the receiver is transmitted and channel information is detected with a degree of distortion of the signal when the signal is received through a channel. This signal is called a pilot signal or a reference signal.

When data is transmitted/received using multiple antennas, the receiver can receive a correct signal only when the receiver is aware of a channel state between each transmit antenna and each receive antenna. Accordingly, a reference signal needs to be provided per transmit antenna, more specifically, per antenna port.

Reference signals can be classified into an uplink reference signal and a downlink reference signal. In LTE, the uplink reference signal includes:

i) a demodulation reference signal (DMRS) for channel estimation for coherent demodulation of information transmitted through a PUSCH and a PUCCH; and

ii) a sounding reference signal (SRS) used for an eNB to measure uplink channel quality at a frequency of a different network.

The downlink reference signal includes:

i) a cell-specific reference signal (CRS) shared by all UEs in a cell;

ii) a UE-specific reference signal for a specific UE only;

iii) a DMRS transmitted for coherent demodulation when a PDSCH is transmitted;

iv) a channel state information reference signal (CSI-RS) for delivering channel state information (CSI) when a downlink DMRS is transmitted;

v) a multimedia broadcast single frequency network (MBSFN) reference signal transmitted for coherent demodulation of a signal transmitted in MBSFN mode; and

vi) a positioning reference signal used to estimate geographic position information of a UE.

Reference signals can be classified into a reference signal for channel information acquisition and a reference signal for data demodulation. The former needs to be transmitted in a wide band as it is used for a UE to acquire channel information on downlink transmission and received by a UE even if the UE does not receive downlink data in a specific subframe. This reference signal is used even in a handover situation. The latter is transmitted along with a corresponding resource by an eNB when the eNB transmits a downlink signal and is used for a UE to demodulate data through channel measurement. This reference signal needs to be transmitted in a region in which data is transmitted.

CoMP (Coordinated Multiple Point Transmission and Reception)

In accordance with the improved system throughput requirements of the 3GPP LTE-A system, CoMP transmission/reception technology (also referred to as Co-MIMO, collaborative MIMO or network MIMO) has recently been proposed. The CoMP technology can increase throughput of a UE located at a cell edge and also increase average sector throughput.

In general, in a multi-cell environment in which a frequency reuse factor is 1, the performance of the UE located on the cell edge and average sector throughput may be reduced due to Inter-Cell Interference (ICI). In order to reduce the ICI, in the legacy LTE system, a method of enabling the UE located at the cell edge to have appropriate throughput and performance using a simple passive method such as Fractional Frequency Reuse (FFR) through the UE-specific power control in the environment restricted by interference is applied. However, rather than decreasing the use of frequency resources per cell, it is preferable that the ICI is reduced or the UE reuses the ICI as a desired signal. In order to accomplish the above object, a CoMP transmission scheme may be applied.

The CoMP scheme applicable to the downlink may be largely classified into a Joint Processing (JP) scheme and a Coordinated Scheduling/Beamforming (CS/CB) scheme.

In the JP scheme, each point (eNB) of a CoMP unit may use data. The CoMP unit refers to a set of eNBs used in the CoMP scheme. The JP scheme may be classified into a joint transmission scheme and a dynamic cell selection scheme.

The joint transmission scheme refers to a scheme for transmitting a PDSCH from a plurality of points (a part or the whole of the CoMP unit). That is, data transmitted to a single UE may be simultaneously transmitted from a plurality of transmission points. According to the joint transmission scheme, it is possible to coherently or non-coherently improve the quality of the received signals and to actively eliminate interference with another UE.

The dynamic cell selection scheme refers to a scheme for transmitting a PDSCH from one point (of the CoMP unit). That is, data transmitted to a single UE at a specific time is transmitted from one point and the other points in the cooperative unit at that time do not transmit data to the UE. The point for transmitting the data to the UE may be dynamically selected.

According to the CS/CB scheme, the CoMP units may cooperatively perform beamforming of data transmission to a single UE. Although only a serving cell transmits the data, user scheduling/beamforming may be determined by coordination of the cells of the CoMP unit.

In uplink, coordinated multi-point reception refers to reception of a signal transmitted by coordination of a plurality of geographically separated points. The CoMP scheme applicable to the uplink may be classified into Joint Reception (JR) and Coordinated Scheduling/Beamforming (CS/CB).

The JR scheme indicates that a plurality of reception points receives a signal transmitted through a PUSCH, the CS/CB scheme indicates that only one point receives a PUSCH, and user scheduling/beamforming is determined by the coordination of the cells of the CoMP unit.

In addition, one case in which there are multiple UL points (i.e., multiple Rx points) is referred to as UL CoMP, and the other case in which there are multiple DL points (i.e., multiple Tx points) is referred to as DL CoMP.

CSI-RS(Channel State Information-reference Signal)

In 3GPP LTE(-A), the antenna port configured to transmit CSI-RS is referred to as a CSI-RS port, and the position of a resource contained in a predetermined resource region in which CSI-RS port(s) transmit(s) the corresponding CSI-RS(s) is referred to as a CSI-RS pattern or a CSI-RS resource configuration. In addition, time-frequency resources through which CSI-RS is allocated/transmitted are referred to as CSI-RS resources. For example, a resource element (RE) used for CSI-RS transmission is referred to as CSI-RS RE. Unlike CRS in which the RE position at which CRS per antenna port is transmitted is fixed, CSI-RS has a maximum of 32 different constructions so as to reduce inter-cell interference (ICI) under a multi-cell environment including a heterogeneous network environment. Different CSI-RS constructions are made according to the number of antenna ports contained in the cell, and contiguous cells may be configured to have different structures. Unlike CRS, CSI-RS may support a maximum of 8 antenna ports (p=15, p=15,16, p=15, . . . ,18, and p=15, . . . ,22), and CSI-RS may be defined only for Δf=15 kHz. The antenna ports (p=15, . . . ,22) may correspond to CSI-RS ports (p=0, . . . ,7), respectively.

CSI-RS configuration may be varies according to the number of CSI-RS ports configured. There are 20 CSI-RS configurations if 2 CSI-RS ports are configured, there are 10 CSI-RS configurations if 4 CSI-RS ports are configured, and there are 5 CSI-RS configurations if 8 CSI-RS ports are configured. Numbers may be assigned to respective CSI-RS configurations defined by the number of CSI-RS ports.

The CSI-RS structures have nested property. The nested property may indicate that a CSI-RS structure for a large number of CSI-RS ports is used as a super set of a CSI-RS structure for a small number of CSI-RS ports. For example, REs configured to construct CSI-RS structure #0 regarding 4 CSI-RS ports are contained in resources configured to construct CSI-RS structure #0 regarding 8 CSI-RS ports.

A plurality of CSI-RSs may be used in a given cell. In the case of non-zero power CSI-RS, only CSI-RS for one structure is transmitted. In the case of zero-power CSI-RS, CSI-RS of a plurality of structures can be transmitted. From among resources corresponding to the zero-power CSI-RS, the UE proposes zero transmit (Tx) power for resources other than resources to be proposed as non-zero power CSI-RS. For example, in the case of a radio frame for TDD, no CSI-RS is transmitted in any one of a special subframe in which DL transmission and UL transmission coexist, a subframe in which a paging message is transmitted, and a subframe in which transmission of a synchronous signal, physical broadcast channel (PBCH) or system information block type1 (SIB1) collides with CSI-RS. The UE assumes that no CSI-RS is transmitted in the above subframes. Meanwhile, time-frequency resources used by the CSI-RS port for transmission of the corresponding CSI-RS are not used for PDSCH transmission, and are not used for CSI-RS transmission of other antenna ports instead of the corresponding CSI-RS port.

Time-frequency resources used for CSI-RS transmission are not used for data transmission, such that a data throughput is reduced in proportion to the increasing CSI-RS overhead. Considering this fact, CSI-RS is not constructed every subframe, and the CSI-RS is transmitted at intervals of a predetermined transmission period corresponding to a plurality of subframes. In this case, compared to the case in which CSI-RS is transmitted every subframe, the amount of CSI-RS transmission overhead can be greatly reduced. The above-mentioned subframe will hereinafter be referred to as a CSI-RS subframe configured for CSI-RS transmission.

A base station (BS) can inform a UE of the following parameters through higher layer signaling (e.g., MAC signaling, RRC signaling, etc.).

-   -   Number of CSI-RS ports     -   CSI-RS structure     -   CSI-RS subframe configuration I_(CSI-RS)     -   CSI-RS subframe configuration period T_(CSI-RS)     -   CSI-RS subframe offset Δ_(CSI-RS)

If necessary, the BS (or eNB) may inform the UE of not only a CSI-RS configuration transmitted at zero power, but also a subframe used for transmission of the zero-power CSI-RS configuration.

CSI-IM(Interference Measurement)

For the 3GPP LTE Rel-11 UE, one or more CSI-IM resource structures may be configured. CSI-IM resource may be used to measure interference. The CSI-RS structure and the CSI-RS subframe structure (ICSI-RS) may be configured through higher layer signaling for each CSI-IM resource.

CSI Report

In a 3GPP LTE(-A) system, a user equipment (UE) reports channel state information (CSI) to a base station (BS) and CSI refers to information indicating quality of a radio channel (or a link) formed between the UE and an antenna port. For example, the CSI includes a rank indicator (RI), a precoding matrix indicator (PMI), a channel quality indicator (CQI), etc. Here, the RI indicates rank information of a channel and means the number of streams received by the UE via the same time-frequency resources. Since the value of the RI is determined depending on long term fading of the channel, the RI is fed from the UE back to the BS with periodicity longer than that of the PMI or the CQI. The PMI has a channel space property and indicates a precoding index preferred by the UE based on a metric such a signal to interference plus noise ratio (SINR). The CQI indicates the strength of the channel and means a reception SINR obtained when the BS uses the PMI.

Based on measurement of the radio channel, the UE may calculate a preferred PMI and RI, which may derive an optimal or best transfer rate when used by the BS, in a current channel state and feed the calculated PMI and RI back to the BS. The CQI refers to a modulation and coding scheme for providing acceptable packet error probability for the fed-back PMI/RI.

A wireless communication system such as LTE receives CSI feedback from a UE to determine a data transmission scheme such as scheduling, precoding or modulation and coding scheme (MCS). For example, in LTE Rel-11, an eNB allocates a CSI-reference signal (RS) for data channel measurement and a CSI-interference measurement (IM) resource for interference measurement to UEs for CSI feedback. In this case, a combination of a single CSI-RS and a single CSI-IM resource may be defined as a CSI process. The UE having received allocation of the CSI process measures spatial characteristics and reception intensity of a received signal based on the CSI-RS, measures spatial characteristics and interference intensity of an interference signal based on the CSI-IM resource, determines a rank indicator (RI), a precoding matrix indicator (PMI) and a channel quality indicator (CQI) of the corresponding CSI process, and reports the determined information to the eNB. In LTE Rel-11, the UE can receive allocation of a plurality of CSI processes to receive data transmitted from a plurality of cells according to a coordinated multiple point transmission/reception (CoMP) scheme. Furthermore, the UE feeds back CSI acquired in every CSI process to the eNB based on an independent period and subframe offset.

For an enhanced wireless communication system such as LTE Rel-12, a network assisted interference cancellation and suppression (NAICS) scheme for removing interference from a neighboring eNB by a UE based on network assistance is under discussion. FIG. 5 illustrates an interference environment in which data transmitted from eNB₁ to UE₁ provides interference to UE₂ while data transmitted from eNB₂ to UE₂ provides interference to UE₁ when UE₁ is served by eNB₁ and UE₂ is served by eNB₂ in an LTE system.

In this case, if UE₁ has NAICS capability, UE₁ may greatly reduce interference on the data of UE₁ by performing NAICS on the data of UE₂. For LTE Rel-12, a scheme for reflecting an effect of removing interference by performing NAICS on a signal received from a specific cell, in CSI by an NAICS UE is under discussion. Hereinafter, for convenience of explanation, the effect of mitigating interference by performing NAICS is referred to as the NAICS effect in the present invention. For example, the NAICS UE detects a neighboring cell interference data transmission scheme at a timing for measuring interference using CSI-IM, through blink detection and reflects an NAICS effect considering the transmission scheme of the corresponding data in CSI feedback.

However, a transmission scheme of interference data at a timing for measuring interference using CSI-IM by the NAICS UE can differ from a transmission scheme of interference data at a timing for scheduling using CSI having interference characteristics of the measurement timing reflected therein, based on, for example, the size of a data packet transmitted from the neighboring cell. For example, a modulation order of the neighboring cell data may be QPSK and a precoding scheme thereof may be P₁ at the measurement timing, but a modulation order of the neighboring cell data may be 16QAM and a precoding scheme thereof may be P₂ at the scheduling timing. Eventually, the NAICS UE may incorrectly predict and reflect an NAICS effect in CSI feedback, thus causing performance degradation.

A description is now given of a CSI feedback scheme considering an NAICS target cell and a neighboring cell interference data transmission scheme assumed to apply an NAICS scheme by a UE, i.e., interference hypothesis (IH), to solve the above problem.

Initially, a serving cell configures an extended CSI process including a signal from the serving cell and a CSI-IM resource indicating that interference from a specific interfering cell is removed, and IH indicating an interference data transmission scheme from the interfering cell, for an NAICS UE. Hereinafter, for convenience of explanation, a combination of a CSI-RS from a serving cell, a CRS or CSI-RS from a neighboring cell, and a single CSI-IM resource is referred to as a “CSI resource set” in this specification. Then, the NAICS UE may virtually calculate an interference covariance matrix for an interference signal from the specific interfering cell after the NAICS effect is reflected, using the CRS or CSI-RS of the CSI resource set based on a transmission scheme (e.g., number of layers, precoding scheme, modulation order) of interference data indicated by the IH and add the interference covariance matrix to an interference covariance matrix for an interference signal from other interference sources measured using the CSI-IM of the CSI resource set, thereby reflecting the NAICS effect for the specific interfering cell in CSI feedback. The above scheme has advantages in that the NAICS effect is virtually reflected based on IH and thus a CSI-IM resource for actually reflecting the IH does not need to be additionally configured. However, in an LTE Rel-11 system according to an embodiment of the present invention, the maximum number of CSI processes is restricted to 4 in consideration of the amount of CSI feedback load of a UE, and this means that the maximum number of CSI feedback loops available to the UE is restricted to 4. Accordingly, if a CSI feedback loop is configured for each combination of a single CSI resource set and a single IH as described above, only up to 4 combinations of NAICS target cell and IH can be considered. If the expressible combinations of NAICS target cell and IH are restricted as described above, the NAICS effect can be restrictively reflected in CSI feedback only when a network uses the corresponding combinations.

Accordingly, the present invention considers a CSI feedback scheme performed by reflecting an NAICS effect for more various combinations of NAICS target cell and IH using a restricted number of CSI processes. Initially, a CSI resource set corresponding to a plurality of NAICS target cells is defined to express the NAICS target cells in a single CSI process, and a UE-driven CSI process including a plurality of CSI resource sets is configured for an NAICS UE. In this case, the NAICS UE dynamically selects a cell having the strongest interference as an NAICS target cell, calculates CSI having the NAICS effect reflected therein, using a CSI resource set corresponding to the selected NAICS target cell, and then feeds back information about the selected CSI resource set together with the CSI to a serving cell. Then, to express a plurality of IHs using a single CSI process, the present invention proposes a method for signaling scheduling restriction information of a neighboring cell as an IH map having a total of L timings each including N IHs to an NAICS UE by a network, and feeding back N types of CSI assuming N IHs configured for each timing of the IH map at the corresponding timing in a CSI process by the NAICS UE. In this case, in consideration of a scheduling restriction application timing to a neighboring cell, the network should additionally signal start and end timings for applying the IH map to the NAICS UE.

Method for Expressing Plural NAICS Target Cells Using Restricted CSI Process

CSI Resource Set

According to another embodiment of the present invention, a network may define a CSI resource set including a CSI-RS of a serving cell, a CRS or CSI-RS of an interfering cell, and a CSI-IM resource to reflect an NAICS effect in CSI, and configure and signal an NAICS CSI process including one or more CSI resource sets to NAICS UEs. Currently, in 3GPP LTE Rel-12, a scheme for adopting a look up table to which an SNR for a serving cell, an INR for an interfering cell, and a transmission scheme (e.g., modulation order) of interference data are input and from which scaling factor a for reducing a power value of the interference signal is output is under discussion as a scheme for expressing mitigation of an interference signal from a specific interfering cell by performing NAICS. In this case, if channel information is acquired using the CRS or CSI-RS and the transmission scheme information (e.g., number of layers, precoding scheme, modulation order) of the interference data, which is specified by the IH or detected through blind detection at a CSI-IM based interference measurement timing, is used, interference power (e.g., interference covariance matrix) may be virtually predicted from a corresponding cell after the NAICS scheme is applied.

UE-driven CSI Process

According to another embodiment of the present invention, a description is now given of a method for configuring a UE-driven CSI process including a plurality of CSI resource sets by a network. According to operation of the present invention, information about a CSI resource set should be included in a CSI process to allow an NAICS UE to reflect an NAICS effect in CSI. In this case, if a CSI process is configured to include only one CSI resource set, an NAICS UE for which the corresponding CSI process is configured can reflect an NAICS effect for only one cell indicated by one CSI resource set in a CSI feedback procedure based on the corresponding CSI process until a new CSI process is configured. Thus, according to the current embodiment, the network may define and configure a UE-driven CSI process including a plurality of CSI resource sets in consideration of a plurality of NAICS target cells, and the NAICS UE may select a CSI resource set corresponding to a desired NAICS target cell to calculate CSI in the UE-driven CSI process. In this case, the NAICS UE may signal UE-selected CSI resource set index information together with CSI feedback information to the network. That is, the UE-selected CSI resource set index information together with one or more of RI, PMI, and CQI among CSI elements may be reported to a serving cell. The above information may be used when the serving cell secondarily processes the CSI feedback information, e.g., CSI averaging.

FIG. 6 illustrates an example in which an NAICS UE performs CSI feedback based on CSI resource set 1 at T₁ and T₂ and performs CSI feedback based on CSI resource set 3 at T₃ when the NAICS UE receives allocation of a UE-driven CSI process including 3 CSI resource sets (e.g., CSI resource sets 1, 2, and 3).

UE-driven CSI Process and IH

According to another embodiment of the present invention, a description is now given of a method for configuring IH per CSI resource set when a UE-driven CSI process including a plurality of CSI resource sets is configured by a network. According to the present invention, to reflect an NAICS effect in CSI feedback by selecting and using a CSI resource set among the CSI resource sets of the UE-driven CSI process, an NAICS UE should be able to check an interference data transmission scheme from an interfering cell corresponding to the selected CSI resource set. Thus, according to the current embodiment, as one method for the above operation, the network may configure IH indicating the interference data transmission scheme per CSI resource set of the UE-driven CSI process. In this case, the NAICS UE for which the UE-driven CSI process is configured selects a CSI resource set corresponding to interference data which currently provides major interference, and performs CSI feedback by reflecting an NAICS effect in CSI based on IH information configured with the corresponding CSI resource set. At this time, if the IH information is not configured with the CSI resource set, the NAICS UE acquires information about interference data selected by the NAICS UE as major interference at a timing corresponding to a CSI-IM resource of the corresponding CSI resource set, through blind detection.

Method for Expressing Plural IHs Using Restricted CSI Process

Scheduling Restriction and IH

According to another embodiment of the present invention, IH corresponding to information about a neighboring cell interference data transmission scheme restricted by scheduling restriction of the neighboring cell may be signaled to an NAICS UE. Reflecting of an NAICS effect in CSI feedback for specific neighboring cell interference by assuming a specific IH is valid when the neighboring cell performs scheduling restriction on a data transmission scheme of the corresponding IH. On the other hand, the interference data transmission scheme restricted by the scheduling restriction of the specific neighboring cell may be signaled to the NAICS UE in the form of IH, and the NAICS UE may determine that no scheduling restriction is present if such information is not indicated by the IH.

IH Map Configuration

According to another embodiment of the present invention, a network may signal scheduling restriction information of a neighboring cell as an IH map having a total of L timings each including N or fewer IHs per neighboring cell capable of being an NAICS target, when the maximum number of CSI processes configurable for an NAICS UE is N. As described above, when a neighboring cell applies scheduling restriction and a serving cell for serving an NAICS UE preliminarily acquires the scheduling restriction information of the neighboring cell, the serving cell preferably gives an indication to the NAICS UE to reflect an NAICS effect considering a transmission scheme of interference data based on scheduling restriction, in CSI feedback before a scheduling timing.

For example, different CSI processes can be configured using different IHs. However, considering that the maximum number of CSI processes is restricted to 4 in an LTE system according to an embodiment of the present invention, the above scheme has disadvantages in that up to 4 IHs can be expressed. That is, the above scheme can be effective when the scheduling restriction of the neighboring cell is expressed using only 4 IHs.

Accordingly, in consideration of more various types of neighboring cell scheduling restriction, the current embodiment proposes a method for signaling scheduling restriction information of a neighboring cell as an IH map having a total of L timings each including N or fewer IHs per neighboring cell capable of being an NAICS target, when the maximum number of CSI processes configurable for an NAICS UE is N. In this case, the network preliminarily signals the scheduling restriction information of the neighboring cell based on time variation to the NAICS UE and thus the NAICS UE does not unnecessarily perform CSI feedback for an IH not applied by the scheduling restriction of the neighboring cell at a specific timing. In this case, the serving cell may additionally signal start and end timings for applying the IH map to the NAICS UE. Alternatively, the IH map may refer to a scheduling restriction pattern which is repeated in a certain cycle.

IH Index and CSI Process Index

According to another embodiment of the present invention, a description is now given of a method for preliminarily signaling correspondence between N IH indexes and N CSI process indexes per IH map to an NAICS UE when the maximum number of CSI processes configurable for the NAICS UE is N. The IH map according to operation of the present invention may configure up to N IHs at each timing. In this case, when a specific timing has M IHs, M CSI feedback loops corresponding to the number of IHs are needed to reflect an NAICS effect based on the IHs in CSI. In this case, even when M CSI processes are present, which one of the M IHs is reflected in which CSI process should be defined. Thus, according to the current embodiment, a serving cell may preliminarily define and signal correspondence between N IH indexes and N CSI process indexes per IH map to an NAICS UE. For example, the IH indexes and the CSI process indexes may sequentially correspond to each other.

According to another embodiment of the present invention, a description is now given of a method for feeding back N types of CSI having an NAICS effect reflected therein based on N IHs configured at a k-th timing of the IH map based on preliminarily defined correspondence between IH indexes and CSI process indexes in N CSI processes at the k-th timing or a CSI feedback timing between the k-th timing and a (k+1)-th timing by an NAICS UE. Based on the IH map proposed by the present invention and correspondence between the IH indexes and the CSI process indexes, as shown in FIG. 7, an IH of a 1-st IH index at the k-th timing may be fed back to a serving cell in a first CSI process at the k-th timing or the CSI feedback timing between the k-th timing and the (k+1)-th timing. For example, when N CSI processes are configured, the NAICS UE may perform CSI feedback for N IH sets which vary based on time.

In this case, the N IHs configured for the k-th timing of the IH map at the k-th timing or the CSI feedback timing between the k-th timing and the (k+1)-th timing may be applied to some types of CSI fed back in the CSI processes. For example, the IHs may be applied only to RI, and PMI and CQI fed back in the same CSI processes as the RI may be configured to follow the IHs assumed for the RI. In this case, each CSI process includes CSI feedback for 1 IH indicated by an IH index corresponding to a CSI process index of the CSI process at one timing, and the content of IH indicated by the IH index may vary by the IH map based on time.

UE-driven CSI Process and IH Map

According to another embodiment of the present invention, the same M CSI resource sets may be shared by N UE-driven CSI processes, a network may preliminarily configure M IH maps corresponding to the M CSI resource sets, and an NAICS UE may select a CSI resource set corresponding to a major interference source and feed back CSI for N or fewer IHs indicated by an IH map corresponding to the selected CSI resource set in a UE-driven CSI process having a CSI process index corresponding to each IH index.

The method simultaneously using the UE-driven CSI processes and the IH maps proposed by the current embodiment may be expressed as illustrated in FIG. 8. Initially, when the NAICS UE selects a CSI resource set corresponding to a major interfering cell thereof, a corresponding IH map is also selected. In this case, each of the N UE-driven CSI processes performs CSI feedback by reflecting IH of the selected IH map indicated by an IH index corresponding to a CSI process index thereof.

Method for Configuring CSI Enabled to Reflect NAICS Effect by Serving Cell

A description is now given of a method for signaling more specific indications for CSI feedback having an NAICS effect reflected therein, to an NAICS UE by a serving cell.

Network Signals CSI Process Enabled to Reflect NAICS Effect

According to another embodiment of the present invention, a network or a serving cell may signal information about whether each CSI process configured for a specific UE is enabled to reflect an NAICS effect. In general, the UE may freely reflect the NAICS effect within a range satisfying a frame error rate (FER) condition in CSI processes other than a UE-driven CSI process proposed by the present invention. However, if a neighboring cell does not support scheduling restriction in a current period and a data packet to be scheduled has a small size (e.g., HTTP), the interference signal characteristics can greatly vary based on time. In this case, even when a UE has NAICS capability (i.e., NAICS UE), if the UE performs CSI feedback by arbitrarily reflecting an NAICS effect, interference characteristics of a CSI calculation timing differ from interference characteristics of a scheduling timing and thus CSI having the NAICS effect reflected therein can distort the actual channel state. Thus, according to the current embodiment, when a serving cell configures a CSI process for a UE having NAICS capability, information about whether the corresponding CSI process is enabled to reflect an NAICS effect is signaled. The information about whether the CSI process is enabled to reflect the NAICS effect may be signaled through higher layer signaling such as RRC signaling when the serving cell configures the CSI process for the NAICS UE.

Signaling of CSI Element Enabled to Reflect NAICS Effect

According to another embodiment of the present invention, a description is now given of a method for signaling information about whether each of CSI elements, i.e., RI, PMI, and CQI, reported in a CSI process is enabled to reflect an NAICS effect by a network. When a serving cell signals only information about whether each CSI process is enabled to reflect an NAICS effect according to operation of the present invention, if the serving cell configures a specific CSI process to be disabled to reflect the NAICS effect, a corresponding NAICS UE may not have a chance to reflect the NAICS effect even in a part of CSI. Alternatively, even when the serving cell configures the specific CSI process to be enabled to reflect the NAICS effect, if the NAICS effect which implies uncertainty is enabled to be reflected in an element, e.g., RI, having a relatively long feedback cycle and a strong influence on overall performance, this is not preferable in terms of stability of CSI feedback. For example, it is assumed that a UE having NAICS capability determines that improvement from Rank 1 to Rank 2 is achievable if the NAICS effect is reflected based on interference characteristics of a specific RI feedback timing. In this case, if interference characteristics are changed until a subsequent RI feedback timing and thus Rank 2 becomes inappropriate, the UE should take a risk of performance degradation according to incorrect RI feedback during the corresponding period. Accordingly, to prevent the above-described operation, the present invention proposes a method for signaling information about whether each of RI, PMI, and CQI elements reported in a CSI process is enabled to reflect an NAICS effect by a serving cell. For example, the serving cell may give an indication not to reflect the NAICS effect in RI, but to reflect the NAICS effect in PMI and CQI.

Signaling of Permissible Range of CSI Element Combination Enabled to Reflect NAICS Effect

According to another embodiment of the present invention, a description is now given of a method for signaling information about whether each of available combinations of CSI elements, i.e., RI, PMI, and CQI, reported in a CSI process is enabled to reflect an NAICS effect by a network. To prevent the above-described case in which a UE having NAICS capability incorrectly determines that improvement from Rank 1 to Rank 2 is achievable if the NAICS effect is reflected based on interference characteristics of a specific RI feedback timing, information about whether each of combinations of RI, PMI, and CQI is enabled to reflect the NAICS effect may be signaled. That is, the NAICS effect may be reflected in combinations of RI, PMI, and CQI if RI has Rank 1 and may not be reflected in combinations of RI, PMI, and CQI if RI has Rank 2. In this case, the UE may select a rank capable of achieving a larger performance gain between a performance gain based on a spatial gain achieved when Rank 2 is selected, and a performance gain based on the NAICS effect achieved when Rank 1 is selected.

Signaling of Subframe and Subband Resources of CSI Feedback Enabled to Reflect NAICS Effect

According to another embodiment of the present invention, a description is now given of a method for configuring subframe and subband resources enabled to reflect an NAICS effect in a CSI process by a network according to an embodiment of the present invention. A neighboring cell may support scheduling restriction only for a restricted region in terms of time and frequency resources. Accordingly, the network may provide information about subframe and subband resources enabled to reflect the NAICS effect in a CSI process enabled to reflect the NAICS effect, to an NAICS UE. Particularly, in the case of a UE-driven CSI process, the information about the subframe and subband resources may be signaled per CSI resource set.

FIG. 9 illustrates operation according to an embodiment of the present invention. FIG. 9 illustrates operation of a terminal 91 or a serving cell or BS 92 on the assumption that the terminal 91 or the serving cell or BS 92 receives interference from specific interference cell(s).

The terminal 91 may receive one or more CSI process configurations including one or more channel state information (CSI) resource sets from the serving cell or BS 92 (S910). The CSI resource set may be associated with the specific interference cell. Furthermore, the CSI resource set may include CSI-reference signal (RS) configuration information of the serving cell, cell-specific RS (CRS) or CSI-RS configuration information of the specific interference cell, and CSI-interference measurement (IM) resource information.

The terminal may detect a dominant interference signal from a received signal and select a CSI resource set corresponding to the dominant interference signal (S920). In addition, the terminal may calculate CSI having interference cancellation capability reflected therein, using the selected CSI resource set or interference hypothesis (IH) information corresponding to the selected CSI resource set (S930). The IH information may include information about an interference signal transmission scheme.

The terminal may report the calculated CSI to the serving cell in a CSI process corresponding to the selected CSI resource set or the IH information (S940).

The IH information may be provided as a map consisting of N or fewer IH elements for L timings.

The terminal may transmit the index of the selected CSI resource set to the serving cell.

The terminal may receive an indicator indicating whether the one or more CSI process configurations are enabled to reflect the interference cancellation capability, from the serving cell.

The terminal may receive information about an individual element of the CSI enabled to reflect the interference cancellation capability for the one or more CSI process configurations, from the serving cell.

Alternatively, the terminal may receive information about a combination of individual elements of the CSI enabled to reflect the interference cancellation capability for the one or more CSI process configurations, from the serving cell.

Otherwise, the terminal may receive information about a time or frequency resource enabled to reflect the interference cancellation capability for the one or more CSI process configurations, from the serving cell. Here, the information about the time or frequency resource may be provided per CSI resource set.

The terminal may receive IH information corresponding to each of the CSI resource sets.

The terminal may receive mapping information between the IH information and the CSI process configurations.

Operation of the terminal is described as an embodiment of the present invention in FIG. 9, and it should be understood by one of ordinary skill in the art that a combination of two or more of the above-described embodiments may be implemented by the terminal.

FIG. 10 is a block diagram of a transmitting device 10 and a receiving device 20 configured to implement exemplary embodiments of the present invention. Referring to FIG. 10, the transmitting device 10 and the receiving device 20 respectively include radio frequency (RF) units 13 and 23 for transmitting and receiving radio signals carrying information, data, signals, and/or messages, memories 12 and 22 for storing information related to communication in a wireless communication system, and processors 11 and 21 connected operationally to the RF units 13 and 23 and the memories 12 and 22 and configured to control the memories 12 and 22 and/or the RF units 13 and 23 so as to perform at least one of the above-described embodiments of the present invention.

The memories 12 and 22 may store programs for processing and control of the processors 11 and 21 and may temporarily storing input/output information. The memories 12 and 22 may be used as buffers. The processors 11 and 21 control the overall operation of various modules in the transmitting device 10 or the receiving device 20. The processors 11 and 21 may perform various control functions to implement the present invention. The processors 11 and 21 may be controllers, microcontrollers, microprocessors, or microcomputers. The processors 11 and 21 may be implemented by hardware, firmware, software, or a combination thereof. In a hardware configuration, Application Specific Integrated Circuits (ASICs), Digital Signal Processors (DSPs), Digital Signal Processing Devices (DSPDs), Programmable Logic Devices (PLDs), or Field Programmable Gate Arrays (FPGAs) may be included in the processors 11 and 21. If the present invention is implemented using firmware or software, firmware or software may be configured to include modules, procedures, functions, etc. performing the functions or operations of the present invention. Firmware or software configured to perform the present invention may be included in the processors 11 and 21 or stored in the memories 12 and 22 so as to be driven by the processors 11 and 21.

The processor 11 of the transmitting device 10 is scheduled from the processor 11 or a scheduler connected to the processor 11 and codes and modulates signals and/or data to be transmitted to the outside. The coded and modulated signals and/or data are transmitted to the RF unit 13. For example, the processor 11 converts a data stream to be transmitted into K layers through demultiplexing, channel coding, scrambling and modulation. The coded data stream is also referred to as a codeword and is equivalent to a transport block which is a data block provided by a MAC layer. One transport block (TB) is coded into one codeword and each codeword is transmitted to the receiving device in the form of one or more layers. For frequency up-conversion, the RF unit 13 may include an oscillator. The RF unit 13 may include Nt (where Nt is a positive integer) transmit antennas.

A signal processing process of the receiving device 20 is the reverse of the signal processing process of the transmitting device 10. Under the control of the processor 21, the RF unit 23 of the receiving device 10 receives RF signals transmitted by the transmitting device 10. The RF unit 23 may include Nr receive antennas and frequency down-converts each signal received through receive antennas into a baseband signal. The RF unit 23 may include an oscillator for frequency down-conversion. The processor 21 decodes and demodulates the radio signals received through the receive antennas and restores data that the transmitting device 10 wishes to transmit.

The RF units 13 and 23 include one or more antennas. An antenna performs a function of transmitting signals processed by the RF units 13 and 23 to the exterior or receiving radio signals from the exterior to transfer the radio signals to the RF units 13 and 23. The antenna may also be called an antenna port. Each antenna may correspond to one physical antenna or may be configured by a combination of more than one physical antenna element. A signal transmitted through each antenna cannot be decomposed by the receiving device 20. A reference signal (RS) transmitted through an antenna defines the corresponding antenna viewed from the receiving device 20 and enables the receiving device 20 to perform channel estimation for the antenna, irrespective of whether a channel is a single RF channel from one physical antenna or a composite channel from a plurality of physical antenna elements including the antenna. That is, an antenna is defined such that a channel transmitting a symbol on the antenna may be derived from the channel transmitting another symbol on the same antenna. An RF unit supporting a MIMO function of transmitting and receiving data using a plurality of antennas may be connected to two or more antennas.

In embodiments of the present invention, a UE serves as the transmission device 10 on uplink and as the receiving device 20 on downlink. In embodiments of the present invention, an eNB serves as the receiving device 20 on uplink and as the transmission device 10 on downlink.

The transmitting device and/or the receiving device may be configured as a combination of one or more embodiments of the present invention.

The embodiments of the present application has been illustrated based on a wireless communication system, specifically 3GPP LTE (-A), however, the embodiments of the present application can be applied to any wireless communication system in which interferences exist.

According to an embodiment of the present invention, since channel state information (CSI) having reflected interference cancellation capability therein is reported, overall system performance may be improved.

The detailed description of the exemplary embodiments of the present invention has been given to enable those skilled in the art to implement and practice the invention. Although the invention has been described with reference to the exemplary embodiments, those skilled in the art will appreciate that various modifications and variations can be made in the present invention without departing from the spirit or scope of the invention described in the appended claims. For example, those skilled in the art may use each construction described in the above embodiments in combination with each other. Accordingly, the invention should not be limited to the specific embodiments described herein, but should be accorded the broadest scope consistent with the principles and novel features disclosed herein.

According to an embodiment of the present invention, overall system performance may be improved by reporting channel state information (CSI) having interference cancellation capability reflected therein.

It will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the spirit or scope of the inventions. Thus, it is intended that the present invention covers the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents. 

What is claimed is:
 1. A method for reporting channel state information (CSI) to which interference cancellation capability is reflected in a wireless communication system, the method being performed by a terminal and comprising: receiving one or more CSI process configurations comprising one or more CSI resource sets from a serving cell, the CSI resource set being associated with a specific interference cell; detecting a dominant interference signal from a received signal; selecting a CSI resource set corresponding to the dominant interference signal; calculating the CSI to which interference cancellation capability is reflected, using interference hypothesis (IH) information corresponding to the selected CSI resource set; and reporting the calculated CSI to the serving cell through a CSI process corresponding to the IH information corresponding to the selected CSI resource set, wherein the CSI resource set comprises: CSI-reference signal (RS) configuration information of the serving cell, cell-specific RS (CRS) or CSI-RS configuration information of the specific interference cell, and CSI-interference measurement (IM) resource information, and wherein the IH information comprises information about a transmission scheme of interference signal, and wherein the IH information is provided for each interference cell, and comprises N or fewer IH elements corresponding to the one or more CSI resource sets for L timings, where N is a maximum number of CSI processes configured for the terminal.
 2. The method according to claim 1, further comprising transmitting an index of the selected CSI resource set to the serving cell.
 3. The method according to claim 1, further comprising receiving an indicator indicating whether the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.
 4. The method according to claim 1, further comprising receiving information about an individual element of the CSI to which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.
 5. The method according to claim 1, further comprising receiving information about a combination of individual elements of the CSI to which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.
 6. The method according to claim 1, further comprising: receiving information about a time or frequency resource in which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell, wherein the information about the time or frequency resource is provided per CSI resource set.
 7. The method according to claim 1, further comprising receiving IH information corresponding to each of the CSI resource sets.
 8. The method according to claim 1, further comprising receiving relationship information between the IH information and the CSI process configurations.
 9. A terminal configured to report channel state information (CSI) in a wireless communication system, the terminal comprising: a radio frequency (RF) unit; and a processor operably connected to the RF unit, and configured to: control the RF unit; receive one or more CSI process configurations comprising one or more CSI resource sets from a serving cell, the CSI resource set being associated with a specific interference cell; detect a dominant interference signal from a received signal; select a CSI resource set corresponding to the dominant interference signal; calculate the CSI to which interference cancellation capability is reflected, using interference hypothesis (IH) information corresponding to the selected CSI resource set; and report the calculated CSI to the serving cell through a CSI process corresponding to the IH information corresponding to the selected CSI resource set, wherein the CSI resource set comprises: CSI-reference signal (RS) configuration information of the serving cell, cell-specific RS (CRS) or CSI-RS configuration information of the specific interference cell, and CSI-interference measurement (IM) resource information, and wherein the IH information comprises information about a transmission scheme of interference signal, and wherein the IH information is provided for each interference cell, and comprises N or fewer IH elements corresponding to the one or more CSI resource sets for L timings, where N is a maximum number of CSI processes configured for the terminal.
 10. The terminal according to claim 9, wherein the processor is further configured to transmit an index of the selected CSI resource set to the serving cell.
 11. The terminal according to claim 9, wherein the processor is further configured to receive an indicator indicating whether the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.
 12. The terminal according to claim 9, wherein the processor is further configured to receive information about an individual element of the CSI to which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.
 13. The terminal according to claim 9, wherein the processor is further configured to receive information about a combination of individual elements of the CSI to which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell.
 14. The terminal according to claim 9, wherein: the processor is further configured to receive information about a time or frequency resource in which the interference cancellation capability is reflected for the one or more CSI process configurations, from the serving cell; and the information about the time or frequency resource is provided per CSI resource set.
 15. The terminal according to claim 9, wherein the processor is further configured to receive IH information corresponding to each of the CSI resource sets.
 16. The terminal according to claim 9, wherein the processor is further configured to receive relationship information between the IH information and the CSI process configurations. 